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Biomedical subjects

L Moens

Publications and source records attributed to L Moens.

At least 91 records · Page 5Linked to original sources
PubMed1978

Oxygen-binding characteristics of three extracellular haemoglobins of Artemia salina.

The oxygen-binding characteristics of the three extracellular haemoglobins of brine shrimp (Artemia salina) were studied in vitro by using highly purified preparations. Haemoglobin I is induced last in the development of brine shrimps when functional gills are formed. It has the lowest oxygen affinity (p(50) 5.34mmHg), an intermediate Bohr effect (ø -0.09 at 20 degrees C) above pH8 and a temperature-sensitivity (DeltaH -44.8 to -45.6kJ/mol at pH8-9) comparable with those observed with other invertebrate haemoglobins [Weber & Heidemann (1977) Comp. Biochem. Physiol. A57, 151-155]. Haemoglobin II, which is the first to be induced, soon after hatching of nauplius larvae, persists generally throughout the whole adult life. It has an intermediate oxygen affinity (p(50) 3.7mmHg), the highest Bohr effect (ø -0.21 at 20 degrees C) above pH8 and a similar temperature-sensitivity (DeltaH -46.0 to -54.8kJ/mol at pH8-9) as haemoglobin I. However, haemoglobin III, which is induced second several hours after the induction of haemoglobin II but disappearing from the haemolymph in the middle of adult life, has the highest oxygen affinity (p(50) 1.8mmHg), the lowest Bohr effect (ø -0.03 at 20 degrees C) above pH8.5 and a high resistance against temperature variation between 10 and 25 degrees C at pH8.5-9 (DeltaH -22.6 to -23.0kJ/mol). At pH7.5-8, haemoglobin III exhibits a similar temperature-sensitivity under 30 degrees C as do other haemoglobins. All three haemoglobins have a rather low co-operativity, with Hill coefficients (h 1.6-1.9 at pH8.5), which are dependent on both pH and temperature. The highest co-operativity was observed at 20 degrees C and pH9 for haemoglobins I and II, whereas it was at 27 degrees C and pH8.5 for haemoglobin III. Thus the oxygen-binding behaviour of haemoglobin III in vitro is significantly different from those of haemoglobins I and II and indicates possibly its specific physiological role in vivo in the adaptive process in the natural environment.

Animals↗
PubMed1978

Evidence for a dimeric form of Artemia salina extracellular hemoglobins with high-molecular-weight subunits.

The brine shrimp, Artemia salina, produces at least three chemically and ontogenetically distinct extracellular hemoglobins (Hb-I, Hb-II and Hb-III). The estimated molecular weights of these hemoglobins are 240000-260000, containing 14 heme groups based on the iron and heme contents of a molar species. Hb-II, which corresponds to a minimal molecular weight of about 18 000 per heme [Moens, L. and Kondo, M. (1977) Biochem. J. 165, 111-119]. Denaturation of the reduced and alkylated hemoglobins with 8 M guanidine hydrochloride revealed apparently one polypeptide chain having a molecular weight of 126 000. Thus a single native hemoglobin molecule should be composed of two of these high-molecular-weight subunits each of which is bound with seven hemes. Upon sodium dodecyl sulfate/polyacryamide gel electrophoresis of either native hemoglobins or isolated subunits it was found that the 126 000-Mr polypeptide was cleaved specifically into two unequally-sized fragments of Mr 50 000 and 80 000. Further denaturation of native hemoglobins with urea at pH 2.5 or 11 followed by sodium dodecyl sulfate gel electrophoresis confirmed these results. The amino acid compositions determined for native Hb-II and its subunit and fragments are found to be very similar, implying that no specifically localized amino acid sequences are present and that the subunit globin chain could be composed of seven similar repeat units (Mr approximately 18 000) being linked covalently to one another. The amino acid compositions of Hb-I and Hb-III showed only minor differences to that of Hb-II.

Amino Acids↗
PubMed1977

Characterization of the extracellular haemoglobins of Artemia salina.

The following factors were measured for extracellular haemoglobins of Artemia salina: a minimal molecular weight of globin chain per haem group (based on the iron and haem contents), the absorption coefficients, the absorption spectra of various derivatives and the amino acid compositions. These were compared with those of the haemoglobins of other invertebrates. Three Artemia haemoglobins (I, II and III) had similar molecular structures, constructed from two-globin subunits of 122000-130000mol.wt. Since the minimal mol.wt. was determined to be 18000, this suggests that one globin subunit was bound by seven haem groups, and hence one haemoglobin molecule (240000-260000mol.wt.) should contain 14 haem groups. A successful identification of this high-molecular-weight subunit required first the denaturation of haemoglobin in 1% sodium dodecyl sulphate before sodium dodecyl sulphate gel electrophoresis. Denaturation by prolonged incubation (12-36 h) at room temperature in the presence of 0.1% sodium dodecyl sulphate [Bowen, Moise, Waring & Poon (1976) Comp. Biochem. Physiol. B55, 99-103] was accompanied by extensive proteolysis, resulting in low recovery of the stainable protein and heterogeneous gel patterns. Regardless of which electrophoretic system was used, the high-molecular-weight subunit was always present provided that 1% sodium dodecyl sulphate was present during denaturation. These results contrast with those obtained by Bowen et al. (1976). However, preferential cleavage of the globin subunit (alpha) seemed to occur in vitro when standard conditions were used, producing two specific fragments having mol.wts. of 80000 (beta) and 50000 (gamma).

Amino Acids↗
PubMed1976

The structure of Artemia salina haemoglobins. A comparative characterisation of four naupliar and adult heamoglobins.

Haemoglobins of Artemia salina were investigated during development and the results obtained are summarised as follows. a)A new haemoglobin (haemoglobin N) was induced de novo in the hatching nauplius, but not in the prenauplius nor in the embryo. b)Haemoglobin N seemed not to be synthesised in the adult. c)The adult contained three distinct haemoglobins (haemoglobins I, II and III) in a quantitative ratio of 1:6:3, respectively, and these haemoglobins were not detected in nauplius. d)Isoelectric points determined were 5.7,5.6,5.7, and 5.9 for haemoglobin N, I, II and III, respectively. e)All four haemoglobins contained one large polypeptide (Mr= 1.1-1.3 X 10(5)) and possibly two minir polypeptides (Mr = 8-9.5 X 10(4) and Mr = 5.4 X qo(4), respectively).

Animals↗